Rate Of Peroxide Formation Research Articles

Controlling factors in the direct formation of H2O2 from H2 and O2 over a Pd/SiO2 catalyst in ethanol

Abstract The direct formation of H2O2 in ethanol over a Pd/SiO2 catalyst has been studied under conditions that yield good selectivities for the peroxide, moderate rates of formation, and concentrations of H2O2 that approach 2 wt.%. Several factors, including the partial pressures of H2 and O2, the presence of protons along with chloride and/or bromide ions, and the reaction temperature significantly affect the rate of H2O2 formation, the selectivity of the reaction, and the loss of palladium from the support. Mass transport, which is a function of a particular system, may also limit the rate of peroxide formation. Halide ions (Cl− or Br−) and protons (derived from H2SO4 in this study) are essential for limiting the combustion reaction; i.e., in the absence of these ions almost no peroxide was formed. A selectivity for H2O2 approaching 80% was achieved using 2 × 10−5 M Br− and 0.12 M H2SO4 with an O2/H2 ratio of 15. Bromide is particularly useful as the halide because it inhibits the loss of Pd from the support. The net formation rate for H2O2 was found to be first order with respect to H2 and zero order with respect to O2. The effects of changing the temperature from 5 to 15 °C were evaluated, and it was observed that the system was most stable at the lowest temperature. As might be expected, the initial rate of peroxide formation and the conversion of H2 was the largest at 15 °C, but as the reaction proceeded the rate of peroxide formation and the selectivity decreased. These results further establish the complexity of this three-phase system that involves a network of reactions and the possibility that the catalyst undergoes change with time.

Evaluation of the antiradical and antioxidant potential of grape extracts

Grape seed and bagasse extract obtained from Narince grape cultivar using different solvent mixtures were assayed for their antioxidant properties. Total phenolic contents of the extracts were determined by the Folin-Ciocalteu method. Antioxidant activities of the extracts at different concentrations were evaluated using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, hydrogen peroxide scavenging and phosphomolybdenum methods. Also the extracts, as natural antioxidants, were assayed during eight weeks storage of refined poppy oil at 70 °C. For this reason peroxide value was used as a criterion to assess the antioxidant activity of grape extracts. The grape seed extracts showed strong antioxidant activity, by measuring their capacity to scavenge DPPH and hydrogen peroxide; to reduce Mo(VI) to Mo (V) and to decrease in the rate of peroxide formation, when compared to bagasse extract. Antioxidant activities of the extracts increased when the extract concentration increased.

Isolation and characterisation of antioxidant components from oregano (Origanum heracleoticum)

SummaryIn this study, Origanum heracleoticum was examined as potential source of phenolic antioxidants. The components of the plant were extracted in a Soxhlet apparatus sequentially with solvents of increasing polarity, specifically with petroleum ether (P), diethyl ether (D) and ethanol (E); the ethanol extract was further fractionated to obtain a diethyl ether (ED) and an ethyl acetate (EEAc) fraction. The activity of the extracts to scavenge 2′2′‐diphenyl‐1‐picrylhydrazyl followed the order ED > E> D > EEAc >> P. Moreover, the antioxidant activity in refined cottonseed oil at a concentration of 500 ppm was monitored through peroxide value measurements and revealed that ED resulted in the highest decrease in the rate of peroxide formation followed by D. Specific flavonoids and rosmarinic acid were detected as the main components of D, ED through HPLC–DAD and HPLC–MS/MS analyses.

Non-thermal plasma-induced photocatalytic degradation of 4-chlorophenol in water

TiO 2 photocatalyst (P-25) (50 mg L −1) was tentatively introduced into pulsed high-voltage discharge process for non-thermal plasma-induced photocatalytic degradation of the representative mode organic pollutant parachlorophenol (4-CP), including other compounds phenol and methyl red in water. The experimental results showed that rate constant of 4-CP degradation, energy efficiency for 4-CP removal and TOC removal with TiO 2 were obviously increased. Pulsed high-voltage discharge process with TiO 2 had a promoted effect for the degradation of these pollutants under a broad range of liquid conductivity. Furthermore, the apparent formation rates of chemically active species (e.g., ozone and hydrogen peroxide) were increased, the hydrogen peroxide formation rate from 1.10 × 10 −6 to 1.50 × 10 −6 M s −1, the ozone formation rate from 1.99 × 10 −8 to 2.35 × 10 −8 M s −1, respectively. In addition, this process had no influence on the photocatalytic properties of TiO 2. The introduction of TiO 2 photocatalyst into pulsed discharge plasma process in the utilizing of ultraviolet radiation and electric field in pulsed discharge plasma process enhanced the yields of chemically active species, which were available for highly efficient removal and mineralization of organic pollutants.

Direct synthesis of hydrogen peroxide from H 2 and O 2 using zeolite-supported Au catalysts

The direct synthesis of hydrogen peroxide from H 2 and O 2 using zeolite-supported Au catalysts is described and their activity is contrasted with silica- and alumina-supported Au catalysts. Two zeolites were investigated, ZSM-5 and zeolite Y. The effect of calcination of these catalysts is studied and it is found that for uncalcined catalysts high rates of hydrogen peroxide formation are observed, but these catalysts are unstable and lose Au during use. Consequently, reuse of these catalysts leads to lower rates of hydrogen peroxide formation. However, catalysts calcined at 400 °C are more stable and can be reused without loss of gold. The use of zeolites as a support for Au gives comparable rates of hydrogen peroxide formation to alumina-supported Au catalysts and higher rates when compared with silica-supported catalysts. prepared using a similar method. Zeolite Y-supported catalysts are more active than ZSM-5-supported catalysts for the stable calcined materials. It is considered that the overall activity of these supported catalysts may be related to the aluminium content as the activity increases with increasing aluminium content.

Antioxidant activities of extracts from Combretum hartmannianum and Guiera senegalensis on the oxidative stability of sunflower oil

This study was carried out to investigate the total phenolic compounds beside the potential antioxidant activity of Guiera senegalensis and Combretum hartmannianum extracts. The content of total phenolics in the extracts was determined spectrometrically according to the Folin-Ciocalteu procedure and calculated as gallic acid equivalents (GAE). The antioxidative activities by beta-carotene linoleic acid and DPPH methods of extracts from Guiera senegalensis leaves, (GSL), Guiera senegalensis roots (GSR) and Combretum hartmannianum leaves (CHL), were evaluated in sunflower oil in the dark at 70°C. Total phenolic compounds were 240.1, 275.6 and 253.4 mg/g respectively. The methanolic extracts of (GSL), (GSR) and (CHL), were markedly effective in inhibiting the oxidation of linoleic acid and subsequent bleaching of s-carotene in comparison with the control. Plants extracts (500 mg) effectively inhibited the formation of peroxides in sunflower oil and showed the highest antioxidative activity compared with 20 mg BHA. The GSL extract is the most effective followed by the GSR and CHL extract. The antioxidant activity of the extracts measured by DPPH free radical showed high reduction of 50% DPPH in CHL extract followed by GSR and GSL. Clear differences were found between the control and sunflower oil containing C. hartmannianum and G. senegalensis extracts or BHA, which decreased and slowed the rate of peroxide formation resulting in lower PVs after 96 h of storage at 70 °C.

Dual Effect of Pyruvate in Isolated Nerve Terminals: Generation of Reactive Oxygen Species and Protection of Aconitase

Generation of reactive oxygen species (ROS) in synaptosomes was investigated in the presence of different substrates. When pyruvate was used as a substrate an increased rate of hydrogen peroxide formation was detected by the Amplex Red fluorescent assay, but aconitase, which is known to be a highly sensitive enzyme to ROS was not inhibited. In contrast, pyruvate exerted a partial protection on aconitase against a time-dependent inactivation that occurred when synaptosomes were incubated in the absence of substrates. Disruption of synaptosomal membranes with Triton X-100 prevented the protective effect of pyruvate. It is suggested that citrate and/or isocitrate formed in the metabolism of pyruvate could be responsible for a partial protection of aconitase. Therefore while pyruvate could have a prooxidant effect it could also exert a protective effect on the aconitase.

Drosophila Lysyl Oxidases Dmloxl-1 and Dmloxl-2 Are Differentially Expressed and the Active DmLOXL-1 Influences Gene Expression and Development

Mammalian lysyl oxidase (LOX) is essential for the catalysis of lysyl-derived cross-links in fibrillar collagens and elastin in the extracellular matrix and has also been implicated in cell motility, differentiation, and tumor cell invasion. The active LOX has been shown to translocate to the nuclei of smooth muscle cells and regulate chromatin structure and transcription. It is difficult to interpret the role of the LOX protein as it is co-expressed with other members of the LOX amine oxidase family in most mammalian cells. To investigate the function of the LOX proteins, we have characterized the Drosophila lysyl oxidases Dmloxl-1 and Dmloxl-2. We present the gene, domain structure, and expression pattern of Dmloxl-1 and Dmloxl-2 during development. In early development, only Dmloxl-1 was expressed, which allowed functional studies. We have expressed Dmloxl-1 in S2 cells and determined that it is a catalytically active enzyme, inhibited by beta-amino-proprionitrile (BAPN), a specific LOX inhibitor. We localized DmLOXL-1 in the nuclei in embryos and in adult salivary gland cells in the nuclei, cytoplasm, and cell surface, using immunostaining and a DmLOXL-1 antibody. To address the biological function of Dmloxl-1, we raised larvae under BAPN inhibitory conditions and over-expressed Dmloxl-1 in transgenic Drosophila. DmLOXL-1 inhibition resulted in developmental delay and a shift in sex ratio; over-expression in the w(m4) variegating strain increased drosopterin production, demonstrating euchromatinization. Our previous data on the transcriptional down-regulation of seven ribosomal genes and the glue gene under inhibitory conditions and the current results collectively support a nuclear role for Dmloxl-1 in euchromatinization and gene regulation.

Minimization of peroxide formation rate in soybean oil by antioxidant combinations

The objective of this work was to minimize peroxide formation rates in refined soybean oil packaged in PVC bottles. The experiment was conducted according to a central composite design for four variables, namely, concentrations of TBHQ, β-carotene and citric acid in the oil, and Tinuvin P ® (UV-absorber) in the bottles. The samples were stored at 1720 lx and 25 °C during 6 months. Peroxide values were measured monthly, and the mean peroxide formation rate (PFR) during storage time was calculated. PFR was highly correlated to odor changes, measured as differences-from-control at the end of storage time. TBHQ was the most effective antioxidant, followed by Tinuvin P ®. β-Carotene impaired the color acceptance of the oil. The following antioxidant ranges were suggested to decrease PFR without promoting oil rejection: 150–200 mg kg −1 of TBHQ, not more than 11 mg kg −1 of β-carotene, 30 mg kg −1 of citric acid, and 3–4 g kg −1 of Tinuvin P.

Direct Synthesis of Hydrogen Peroxide from H2 and O2 Using Pd and Au Catalysts.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Direct synthesis of hydrogen peroxide from H2 and O2 using Pd and Au catalysts

The direct synthesis of hydrogen peroxide from H2 and O2 using a range of supported metal catalysts is described and discussed. A detailed study of the factors influencing the formation and decomposition of hydrogen peroxide is presented for a Pd/sulfonated carbon catalyst in a methanol/water solvent. The use of low temperatures (1–2 °C) and short reaction (residence) time are identified as the key factors that favour high selectivity to hydrogen peroxide. Decomposition of hydrogen peroxide, mainly via further hydrogenation, prevents the formation of high concentrations of hydrogen peroxide. Combustion of hydrogen to water is a competing reaction that becomes significant at higher temperatures, but this can be partially inhibited by the addition of HBr. A second set of supported Pd and Au catalysts are evaluated for the direct synthesis of hydrogen peroxide using supercritical CO2 as a solvent. The use of supercritical CO2 is shown to be beneficial when compared with hydrogen peroxide formation at a temperature just below the critical temperature for CO2. However, at the critical temperature of CO2 (31.1 °C), the decomposition of hydrogen peroxide is rapid and only low rates of hydrogen peroxide formation are observed. At low temperature (2 °C) supported Au catalysts are shown to be very selective for the synthesis of hydrogen peroxide. The rate of hydrogen peroxide synthesis is enhanced markedly when Pd is present with Au and a detailed scanning transmission electron microscopy study shows that the 2–9 nm metal nanoparticles present in this supported catalyst are a Au∶Pd alloy.

Peroxide formation in polysorbate 80 and protein stability

Nonionic surfactants are widely used in the development of protein pharmaceuticals. However, the low level of residual peroxides in surfactants can potentially affect the stability of oxidation‐sensitive proteins. In this report, we examined the peroxide formation in polysorbate 80 under a variety of storage conditions and tested the potential of peroxides in polysorbate 80 to oxidize a model protein, IL‐2 mutein. For the first time, we demonstrated that peroxides can be easily generated in neat polysorbate 80 in the presence of air during incubation at elevated temperatures. Polysorbate 80 in aqueous solution exhibited a faster rate of peroxide formation and a greater amount of peroxides during incubation, which is further promoted/catalyzed by light. Peroxide formation can be greatly inhibited by preventing any contact with air/oxygen during storage. IL‐2 mutein can be easily oxidized both in liquid and solid states. A lower level of peroxides in polysorbate 80 did not change the rate of IL‐2 mutein oxidation in liquid state but significantly accelerated its oxidation in solid state under air. A higher level of peroxides in polysorbate 80 caused a significant increase in IL‐2 mutein oxidation both in liquid and solid states, and glutathione can significantly inhibit the peroxide‐induced oxidation of IL‐2 mutein in a lyophilized formulation. In addition, a higher level of peroxides in polysorbate 80 caused immediate IL‐2 mutein oxidation during annealing in lyophilization, suggesting that implementation of an annealing step needs to be carefully evaluated in the development of a lyophilization process for oxidation‐sensitive proteins in the presence of polysorbate. © 2002 Wiley‐Liss Inc. and the American Pharmaceutical Association J Pharm Sci 91:2252–2264, 2002

Influence of particles on sonochemical reactions in aqueous solutions

Numerous publications deal with the possible application of ultrasound for elimination of organic pollutants as a tool for water pollution abatement. Most of the experiments were performed in pure water under laboratory conditions. For developing technologies that hold promise it is necessary to investigate the effect of ultrasound in natural systems or waste water where particulate matter could play an important role. In this paper the influence of quartz particles (2–25 μm) on the chemical effects of ultrasound in aqueous system using a high power ultrasound generator (68–1028 kHz, 100 W, reactor volume 500 ml) is reported. In pure water in dependence on particle size, concentration and frequency the formation rate of hydrogen peroxide under Ar/O 2 (4:1) shows a maximum using 206 kHz in presence of 3–5 μm quartz particles (4–8 g/l). Under these conditions the yield of peroxide is higher than without quartz. Additionally under N 2/O 2 (4:1) besides hydrogen peroxide the formation of nitrite/nitrate was measured. Compared to pure water quartz particle depressed the formation of nitrite/nitrate up to 10-fold but not the formation of H 2O 2. According to the results of H 2O 2 formation the elimination of organic compounds by sonolysis (206 kHz) and the influence of quartz particles were investigated. As organic compounds salicylic acid, 2-chlorobenzoic acid and p-toluenesulfonic acid were used. The influence of quartz on the oxidation of organic compounds (206 kHz) is similar to that on the formation of H 2O 2.

The Antioxidant Property of Aframomum danelli Spice in Oils.

A study was carried out on the antioxidant property of Aframomum danelli extract in palm oil and soybean oil. The activity of A. danielli extract was compared with those of other antioxidants of other plant sources, rosemary extract and d- tocopherol, at different concentrations. A. danielli was as active as rosemary plant extract in reducing rate of peroxide formation in soybean oil at concentrations of 200 ppm and 300 ppm . A danielli was much more effective than tocopherol in reducing peroxidation in soybean oil and palm oil at the higher concentrations except at 50 ppm. The Journal of Food Technology in Africa Volume 6 No.4, 2001, pp. 135-137 KEY WORDS: Antioxidant activity, Aframomum danielli spice, oils.

Photochemical Transformation of Benzil Pendant Groups of Polystyrene Copolymers into Benzoyl Peroxide Moieties and Their Subsequent Thermal Decomposition. Cross-Linking or Chain Scission?

Films of the copolymer, 11 wt % 1-{4-(2-methacroyloxyethoxyphenyl}-2-phenyl-1,2-ethanedione (BZMA) and styrene (S) (BZMA/S), as well as polystyrene (PS) doped with either the BZMA monomer (BZMA-PS) or 1-{4-(2-acetyloxyethoxy-phenyl}-2-phenyl-1,2-ethanedione (BZAc-PS) in concentrations that match the composition of the copolymer, have been irradiated (λ > 400 nm) in the presence of molecular oxygen at ambient temperatures. The rates of consumption of BZMA and BZAc and the concurrent formation of the corresponding benzoyl peroxide-containing units (BPMA and BPAc) were followed by infrared spectroscopy. The rates of benzil-group consumption and peroxide formation matched each other and were virtually the same in the three film types. Larger concentrations of oxygen increased the rate of consumption of BZMA. From a kinetic treatment of data at two concentrations of oxygen in PS, it is concluded that BZMA photooxidation is more than 10 times faster than that of benzil. At 91 °C, the first-order rate constants ...

Hydrogen peroxide formation: The interaction of ultraviolet radiation and dissolved organic carbon in lake waters along a 43–75°N gradient

Hydrogen peroxide (H2O2) formation rates (nM h−1), photoproductive capacity (nM W−1 h−1 m−2), and H2O2 formation efficiency (ϕH2O2) were measured on water samples exposed to a standard light source with a spectral composition similar to natural sunlight. Samples were from lakes and wetlands with varying levels of dissolved organic C (DOC), P, Fe, Ca, and pH. The relationship between H2O2 formation rates and DOC was a power function (H2O2 = 49.65 DOC1.71; r2 = 0.94), whereas the relationships between formation rates and DOC fluorescence (DOCFL) (H2O2 = 118.32 + 33.06 DOCFL; r2 = 0.98) and absorption coefficients at 310 (Ka310) were linear (H2O2 = 185.0 + 55.50 Ka310; r2 = 0.91). ϕH2O2 was independent of DOC (r2 = 0.12). Apparent quantum yields decreased with increasing wavelengths (300–400 nm). However, when apparent quantum yields were corrected with solar irradiance data, values were greatest in the UV‐A (320–400 nm) region. The patterns observed were consistent for samples from temperate to arctic regions.

ASCORBIC ACID GLYCATION OF LENS PROTEINS PRODUCES UVA SENSITIZERS SIMILAR TO THOSE IN HUMAN LENS

Soluble calf lens proteins were extensively glycated during a 4 week incubation with ascorbic acid in the presence of oxygen. Amino acid analysis of the dialyzed proteins removed at weekly intervals showed an increasing loss of lysine, arginine and histidine, consistent with the extensive protein cross-linking observed. Irradiation of the dialyzed samples with UVA light (1.0 kJ/cm2 total illumination through a 338 nm cutoff filter) caused an increasing loss of tryptophan, an additional loss of histidine and the production of micromolar concentrations of hydrogen peroxide. No alteration in amino acid content and no photolytic effects were seen in proteins incubated without ascorbic acid or in proteins incubated with glucose for 4 weeks. The rate of hydrogen peroxide formation was linear with each glycated sample with a maximum production of 25 nmol/mg protein illuminated. The possibility that the sensitizer activity was due to an ascorbate-induced oxidation of tryptophan was eliminated by the presence of a heavy metal ion chelator during the incubation and by showing equivalent effects with ascorbate-incubated ribonuclease A, which is devoid of tryptophan. The ascorbate-incubated samples displayed increasing absorbance at wavelengths above 300 nm and increasing fluorescence (340/430) as glycation proceeded. The spectra of the 4 week glycated proteins were identical to those obtained with a solubilized water-insoluble fraction from human lens, which is known to have UVA sensitizer activity. The incubation of lens proteins with dehydroascorbic acid or L-threose, but not fructose, produced equivalent glycation, protein crosslinking and sensitizer activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteria in human mouths involved in the production and utilization of hydrogen peroxide

Earlier studies have demonstrated that pure cultures of oral streptococci produce hydrogen peroxide but none has found any free peroxide in dental plaque or salivary sediment despite streptococci being major components of their mixed bacterial populations. The absence of peroxide in plaque and sediment could be due to the dominance of its destruction over its formation by bacterial constituents. To identify which of the oral bacteria might be involved in such a possibility, pure cultures of 27 different oral bacteria were surveyed (as well as dental plaque and sediment) for their peroxide-forming and peroxide-removing capabilities. Peroxide production was measured for each of the pure cultures by incubation with glucose at low and high substrate concentrations (2.8 and 28.0 mM) for 4 h and with the pH kept at 7.0 by a pH-stat. Removal of hydrogen peroxide was assessed in similar experiments where peroxide at 0, 29.4, 147.2 or 294.4 mM [0, 0.1, 0.5 and 1 % (w/v)] replaced the glucose. Hydrogen peroxide formation was seen with only three of the bacteria tested, Streptococcus sanguis I and II (sanguis and oralis), and Strep. mitior (mitis biotype I); levels of hydrogen peroxide between 2.2 and 9.8 mM were produced when these micro-organisms were grown aerobically and 1.1 and 3.9 mM when grown anaerobically. Earlier reports indicate that such levels were usually sufficient to inhibit the growth of many plaque bacteria. The amounts formed were similar at the two glucose levels tested, suggesting that maximum peroxide production is reached at low glucose concentration. None of the three peroxide-pro ducing organisms was able to utilize hydrogen peroxide but five of the other 24 tested, Neisseria sicca, Haemophilus segnis, H. parainfluenzae, Actinomyces viscosus and Staphylococcus epidermidis, could readily do so, as could the mixed bacteria in salivary sediment and dental plaque, both of which contain relatively high numbers of these peroxide-utilizing micro-organisms. The ability of the bacteria in plaque and sediment to degrade hydrogen peroxide was considerable and extremely rapid; peroxide removal was usually complete within the first 15 min of the incubation even when its initial level was as high as 294.4 mM. This almost overwhelming ability to remove peroxide was confirmed when peroxide-producing and -using cultures were mixed and when each of eight salivary sediments was incubated with glucose and with peroxide at concentrations up to 294.4 mM. In the glucose incubations, no hydrogen peroxide was observed, indicating dominance of microbial peroxide removers over hydrogen peroxide producers. In the peroxide incubations, the 294.4 mM concentration was the only one high enough to exceed the removal capacity of some of the sediments, a level that would only occur orally if provided in a therapeutic product. The optimum pH for the production of peroxide ranged between 4.0 and 7.0. The optimum pH for hydrogen peroxide removal ranged between 6.0 and 8.0. This suggests that for any peroxide accumulation to occur, an acidic rather than a neutral or alkaline pH might be more favourable. When glucose was replaced by galactose, a sugar readily available from salivary glycoprotein for oral microbial fermentation, the three peroxide-producing bacteria identified still produced peroxide but at slower rates than with glucose. Also, but unlike with glucose, more peroxide production was observed with 28.0 than with 2.8 mM galactose. These observations are consistent with fermentation of galactose being slower than that of glucose, and probably as a result the tendency to reach a less than maximum rate of peroxide formation with galactose than with glucose. When l(+) lactate, an intermediate or product formed in many oral bacterial fermentations, was supplied as substrate, only the streptococci identified in this study produced peroxide. The amounts and pattern of generation with all three micro-organisms were similar to those seen previously with glucose. Collectively, the findings were consistent with peroxide being produced when pyruvate, arising from either glucose or lactate, is converted aerobically to acetate and carbon dioxide and with this step being rate-limiting when glycolysis is rapid, as readily occurs with glucose but not with galactose.

On the HO2 + HO2 reaction: Its misapplication in atmospheric chemistry models

The self‐reaction of the HO2 radical is an important termination reaction for HOχ and it is the major gas phase source of hydrogen peroxide in the atmosphere. It is well established that the rate of this reaction is sensitive to both pressure and water vapor concentrations. The NASA recommended rate parameter (DeMore et al., 1992) has been utilized in several detailed gas phase chemical mechanisms for modeling the troposphere, but several other recent studies have omitted one or both of the terms for the rate constant. If both the pressure and the water dependent terms are omitted the relative error can be as high as 75% at the surface to near 30% at 10 km for water vapor saturated conditions. Models which omit these terms will predict incorrect HOχ budgets, underestimate gas phase hydrogen peroxide formation rates, and overestimate ozone and organic peroxide formation rates especially in clouds or under marine conditions.

Influence of Dietary Pectin on the Hepatic Levels of Reduced Glutathione and on Lipid Peroxide Formation in Mice.

In order to establish if dietary pectin could influence the levels of hepatic reduced glutathione (GSH) and the rate of lipid peroxide formation, we fed 8 male Balb C mice for 14 days with a standard powder diet supplemented with 5% highly methoxylated apple pectin. Another 8 mice received the standard powder diet only and served as controls. The animals were killed on the 15th day. The levels of GSH and lipid peroxides expressed in terms of malondialdehyde (MDA) were determined in liver homogenates. Besides, parameters that could be related to GSH metabolism or lipid peroxidation, such as the activity of y-glutamyl transferase (γ-GT) and the content of iron, were assessed as well. In pectin-fed animals γ-GT activity was decreased (p<0.01), whereas the level of hepatic GSH was elevated (p<0.001). A negative correlation was established between both parameters. GSH correlated also negatively with lipid peroxides, which were reduced. Iron content was only slightly decreased. The data obtained suggest that the pectin-enriched diet could influence the antioxidant processes in the liver, increasing GSH levels (at least partially by lowering γ-GT activity) and reducing the formation of lipid peroxides.